1. Field of the Invention
This invention relates in general to vibrational energy isolators, and in particular, wire rope isolators. More specifically, but without restriction to the particular embodiment hereinafter described in accordance with the best mode of practice, this invention relates to wire rope vibration isolators employing a minimum of one asymmetric mounting block retaining a disconnected wire rope shaped into an asymmetric loop design.
2. Background of the Prior Art
Excessive vibrational energy can damage and/or cause the deterioration of sophisticated machinery. In industries in which movement is inherent in daily operations, such as avionics and shipping, the need to minimize unwanted vibrational energy is imperative. These industries have come to rely heavily on sensitive electronic equipment, like navigational computers, to maintain daily operations. Constant jostling of electronic equipment can cause system failures that lead to costly downtime to replace and/or repair the damaged equipment.
Over the years, many devices have been designed to isolate damaging vibrations and isolate unwanted kinetic energy. These devices use the unwanted kinetic energy to move simple machinery, like pistons and springs, so as to divert the energy from shock-sensitive equipment attached to the isolator. A good example of a member of this class of devices is the wire rope isolator. The most common wire rope isolators employ a helical wire cable secured between a pair of retaining members. When the isolator is in use, vibrational energy causes the wire rope coil to move in a spring-like fashion, which in turn moves the retaining members vertically toward each other. This movement diminishes the degree of vibrational energy transferred to the affixed sensitive equipment.
The art of wire rope vibration isolators has been contributed to by a number of proposed devices detailed in U.S. Pat. No. 5,549,285 issued to Collins and U.S. Pat. Nos. 5,441,243 and 5,791,636 both issued to Loziuk. These patents describe vibrational energy energy isolators that consist of coiled wire ropes secured between two parallel retaining blocks. Holes drilled into the retaining blocks maintain the helical shape of the wire rope. Vibrational energy causes the wire rope coil to contract which in turn moves the entrapment blocks vertically relative to each other thus absorbing vibrational energy in the process.
There are disadvantages with the helical design. Conventional helical wire rope isolators are ineffective when the support load is a few pounds. In addition, helical wire rope isolators are not well suited for applications with spatial restrictions or significant weight limitations due to the need that the wire coil be of a certain length to be functional. It was therefore desirable to design a wire rope isolator that overcame the limitations associated with traditional helical wire rope isolators. U.S. patent application Ser. No. 09/496,688, incorporated herein by reference, discloses a wire rope vibration isolator that includes a pair of mounting blocks spaced apart by wire rope manipulated into four U-shaped bights. The bights form a cloverleaf-type pattern between the two blocks. To maintain the bight formation, the mounting blocks are crimped into locking contact with the wire rope. When exposed to vibrational energy, the wire rope bights flex causing the mounting blocks to move toward each other expending the unwanted energy in the process.
The wire rope isolator disclosed in U.S. application Ser. No. 09/496,688 successfully solves the problems associated with traditional helical wire rope isolators. The disclosed isolator is capable of supporting relatively light loads. Due to the simpler design, relatively small-scale wire rope isolators can be constructed for applications having limited space. Manufacturing costs are decreased due to ability to use cheaper materials.
It was discovered, however, that applying a tension force to the wire rope during the crimping process reduced dimensional and stiffness variation in the isolator. The design disclosed in the '688 application employs a continuous loop of wire rope having both ends located in the same hole thus prohibiting the use of a tensile force during the crimping process. It was found that locating both ends of the wire rope in the same retaining hole unnecessarily complicated the manufacturing of the isolator, thus increasing production costs. Accordingly, it is highly desirable to design a wire rope vibrational energy isolator with all of the attributes of the design disclosed in U.S. patent application Ser. No. 09/496,688 while maintaining tensile force in the wire rope during manufacture so that dimensional and stiffness qualities are uniform throughout the isolator.